The invention involves a process for controlling the rotational speed of a drive motor.
Processes for controlling the rotational speed of a drive motor, in particular, during the start up period, in a drive train, in particular for use in motor vehicles, including at least one drive motor and a start up element that can be coupled with it, at least indirectly, are known in a multitude of different embodiments with regard to the variables triggering the controlling operation, i.e. the input variables of the control device, the dependence of the control variables on other variables and the correcting variables. It is generally known that, in drive trains of motor vehicles, including an intemal combustion engine, especially Otto or diesel engines, and a start up element that can be mechanically or hydrodynamically coupled to them, as a correcting variable for the rotational speed control of the drive motor, a variable is formed that at least indirectly characterizes the adjustment of the power output stage of the drive motor—throttle valve or injection nozzle—and the adjustment device—throttle valve or injection nozzle—is triggered in this way. Reference is made to, as a representative example, “Diesel injection technology” by Bosch, VDI-Publishers 1993, pages 162-on. Start up period is understood here to be the time span of the operating period of the drive train, which is characterized by a run-up of the drive unit from the start, i.e. the start up of the drive motor until the change into a higher gear level in bypassing the hydrodynamic starter element.
When hydrodynamic couplings are used as a start up element in motor vehicles, they are designed in such a manner that a filling of the hydrodynamic coupling can occur automatically during the start up period, for example, depending on the rotational speed of the drive motor or retarded from it. However, it has been shown that dynamic systems behavior becoming set in this way, characterized by the characteristic line of the coupling, is characterized in that high torque can only be transferred at high rotational speeds of the drive motor. This means, however, for embodiment of the drive motor as an internal combustion engine, that the consumption-optimized range in the performance characteristics of the motor, and thus an operating method that is low in hazardous materials, is not achieved and furthermore, for the transfer of high torque a correspondingly high power drive motor is always necessary.